Hydrofluoroalkanesulfonic acids and salts from fluorovinyl ethers

ABSTRACT

Hydrofluoroalkanesulfonates of the general formula R—O—CXH—CX 2 —SO 3 M, where R is selected from the group consisting of alkyl groups, functionalized alkyl groups, and alkenyl groups; X is selected from the group consisting of hydrogen and fluorine with the proviso that at least one X is fluorine; and M is a cation, are made by reacting fluorovinyl ether with aqueous sulfite solution. Organic onium hydrofluoroalkanesulfonates are useful as ionic liquids and photoacid generators.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is in the field of strong acids useful for catalysis, andtheir salts.

2. Description of Related Art

Trifluoromethanesulfonic acid (TFMSA) is used for catalysis where astrong acid is needed. It offers a safer, more easily handledalternative to the inorganic acids, hydrogen fluoride and sulfuric acid,which are widely used in industrial processes. In addition, because ofits low molecular weight, trifluoromethanesulfonic acid is relativelyvolatile, a disadvantage in high temperature processes. Knownhydrofluoroalkanesulfonic acids, such as1,1,2,2-tetrafluoroethanesulfonic acid (TFESA) and1,1,2,3,3,3-hexafluoropropanesulfonic acid (HFPSA), are made fromtetrafluoroethylene and hexafluoropropylene, respectively, and aresomewhat higher in molecular weight and therefore have lower volatility,but for still less volatile hydrofluoroalkanesulfonic acids highermolecular weight fluoroolefins would be needed. There are few suchfluoroolefins of commercial importance and consequently of readyavailability.

Furthermore, salts of TFMSA have utility as photoacid generators andionic liquids. Those having having a photoactive cationic moiety areuseful photoacid generators for microlithography. In the process ofmicrolithography, molecules called “photoacid generators” (PAGs) areused to capture photons of light and generate protons. The PAG plays animportant role in the imaging process for both positive- andnegative-working chemically amplified resists, because the PAG governslight response properties, such as absorption of light or quantum yieldof acid formation. In addition, the PAG governs the properties of theproduced acid, such as acid strength, mobility, and volatility.

Useful PAGs include organic onium salts, e.g., iodonium salts andsulfonium salts, with non-nucleophilic anions. Organic onium saltsproducing trifluoromethane sulfonic acids upon exposure have beenparticularly preferred, because superior sensitivity and good ultimateresolution of the photoresist system can be obtained. In addition, thesePAGs are known to reduce the formation of insolubles (“scum”) on thesubstrate or at the substrate/resist interface. A known drawback of suchPAGs is that minor quantities of the rather volatiletrifluoromethanesulfonic acid (TFSA) produced during the irradiationprocess may evaporate (outgas) from the photoresist film and causecorrosion of the exposure and process equipment. In addition, it isknown that resist materials containing PAGs that produce TFSA tend toproduce the so-called T-shaped pattern profiles, and show linewidthchanges upon process delays due to the high volatility and the diffusionproperties of this acid.

In summary, the minor quantities of TFMSA produced from the salt canoutgas, causing corrosion to process equipment. Volatility is alsorelated to the rate of diffusion of the acid. Diffusion is anundesirable property in microlithography.

U.S. Pat. No. 6,358,665 discloses onium salt precursors, Y+ASO3-, whichgenerate a fluorinated alkanesulfonic acid. Y represents (R¹)(R²)(R³)S⁺or (R⁴)(R⁵)I⁺ and A represents CF3CHFCF2 or CF3CF2CF2CF2.

WO 02/082185 discloses photoacid compounds with the general structureR—O(CF₂)_(n)SO₃X, where n is an integer between about 1 to 4; X isselected from the group consisting of organic cations and covalentlybonded organic radicals; and suitable R groups include substituted orunsubstituted C1-C12 linear or branched alkyl groups and substituted orunsubstituted perfluoroalkyl groups.

There is a need for hydrofluoroalkanesulfonates andhydrofluoroalkanesulfonic acids of higher molecular weight, for use incatalysis, in ionic liquids and in photoacid generators. It would beparticularly advantageous for such hydrofluoroalkanesulfonates to bepreparable from readily available starting materials.

BRIEF SUMMARY OF THE INVENTION

The present invention provides hydrofluoroalkanesulfonates of thegeneral formula R—O—CXH—CX₂—SO₃M, where R is selected from the groupconsisting of alkyl groups, functionalized alkyl groups, and alkenylgroups; X is selected from the group consisting of hydrogen and fluorinewith the proviso that at least one X is fluorine; and M is a cation.

The present invention also provides a process for manufacture ofhydrofluoroalkanesulfonates of the general formula R—O—CXH—CX₂—SO₃M,where R is selected from the group consisting of alkyl groups,functionalized alkyl groups, and alkenyl groups; X is selected from thegroup consisting of hydrogen and fluorine with the proviso that at leastone X is fluorine; and M is a cation, comprising contacting a vinylether of the formula R—O—CX═CX₂, with sulfite in an aqueous solutionadjusted to about pH 4 to pH 12, and recovering thehydrofluoroalkanesulfonate. In accordance with a preferred aspect of theof the invention, the hydrofluoroalkanesulfonate is reacted with acidwhen the hydrofluoroalkanesulfonic acid is desired as the final product.Preferably this is accomplished by recovering thehydrofluoroalkanesulfonate from the aqueous solution containinghydrofluoroalkanesulfonate as a solid, treating the solid with oleum,and distilling hydrofluoroalkanesulfonic acid therefrom.

The invention also provides a compound of the formula R—O—CXH—CX₂—SO₃M,where R is selected from the group consisting of alkyl groups,functionalized alkyl groups, and alkenyl groups; X is selected from thegroup consisting of hydrogen and fluorine with the proviso that at leastone X is fluorine; and M is organic onium. Compounds in accordance withthis form of the invention are useful as ionic liquids and photoacidgenerators.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that fluorovinyl ethers of the general formulaCF₂═CF—OR, react with aqueous sulfite to yieldhydrofluoroalkanesulfonates. The reaction, represented as the reactionof a perfluorovinyl ether with sulfite, is:R—O—CF═CF₂+SO₃ ⁼+H₂O->R—O—CHF—CF₂SO₃ ⁻+OH⁻  (1)Though (1) is the principal adduct, the hydration reaction (2) is alsoseen in minor amount (0.1-3%).R—O—CF═CF₂+H₂O->R—O—CFH—CF₂OH  (2)The hydration product in (2) further hydrolyzes to form the carboxylicacid:R—O—CFH—CO₂H.  (3)

R represents: (A) alkyl. Alkyl means hydrocarbon group, which may besubstituted with halogen and, if so substituted, preferably the halogenis fluorine or chlorine, preferably alkyl is fluoroalkyl, and morepreferably is perfluoroalkyl. Alkyl may be linear or branched, orcyclic. Preferably, alkyl is linear alkyl. The alkyl group R may containone or more ether linkages. Preferably, the alkyl group has 1 to 20carbon atoms. These fluorovinyl ethers are preferably trifluoro(alkylvinyl ethers). Preferred fluorovinyl ethers are perfluoro(alkyl vinylethers) (PAVE) such as perfluoro(methyl vinyl ether) (PMVE),perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether)(PPVE). Members of this class of fluorovinyl ethers are referred toherein as nonfunctional fluorovinyl ethers.

R also represents: (B) a functionalized alkyl group, i.e., an alkylgroup as defined above which contains a functional group. By functionalgroup is meant a group that confers, or is capable of conferring, suchas after hydrolysis or other treatment, significant reactivity, such asionic character, hydrogen-bonding character, or strongly polarcharacter, such as dipolar character. By strongly polar is meantpolarity greater than that of carbon-hydrogen, or carbon-halogen bonds.Examples of such functional groups are hydroxyl (—OH) or —CH₂OH;carboxyl (—COO⁻) including carboxylic ester, amide, acid, or salt;sulfonate (—SO₃) including sulfonyl halide, preferably fluoride,sulfonic acid, sulfonamide, or sulfonate salt; phosphonate (—P(O)O₂ ⁻),including phosphonic acid or salt; cyanide (—CN). Other possiblefunctional groups are glycidyl, cyanate (—OCN) and carbamate (—O—NH—R′),where R′ is an alkyl group, preferably methyl, with the understandingthat such groups may undergo partial or complete hydrolysis under theconditions of the reaction with sulfite. These fluorovinyl ethers arepreferably trifluoro(alkyl vinyl ethers). Apart from the functionalgroup(s), these functional fluorovinyl ethers are preferablyperfluorovinyl ethers, i.e., R′ is perfluorinated. Members of this classof fluorovinyl ethers are referred to herein as functional fluorovinylethers.

Preferred classes of functional vinyl ethers are:

-   CF₂═CF—(OCF₂CF(CF₃))_(n)(O)_(p)(CF₂)_(m)—Z, where p is 0 or 1, m is    0 to 10 and n is 1 to 20, provided that when m is 0, p is 0, and    further provided that when m is greater than 0, p is 1, and Z is a    functional group such as —CH₂OH, carboxyl (—COO⁻) including    carboxylic ester, amide, acid, or salt; sulfonate (—SO₃ ⁻) including    sulfonyl halide, preferably fluoride, sulfonic acid, sulfonamide, or    sulfonate salt; phosphonate (—O—P(O)O₂ ⁻), including phosphonic    acid, acid halide, or salt; glycidyl; cyanide (—CN); cyanate, and    carbamate.-   CF₂═CF—O—Y—CF₂—Z, where Y is alkylene, preferably fluoroalkylene,    and more preferably perfluoroalkylene and may be cyclic and may    include one or more ether oxygens, and is most preferably CF₂, and Z    is a functional group such as —CH₂OH, carboxyl (—COO⁻) including    carboxylic ester, amide, acid, or salt; sulfonate (—SO₃ ⁻) including    sulfonyl halide, preferably fluoride, sulfonic acid, sulfonamide, or    sulfonate salt; phosphonate (—O—P(O)O₂ ⁻), including phosphonic    acid, acid halide, or salt; glycidyl; cyanide (—CN); cyanate, and    carbamate.

Examples of such functional vinyl ethers from the patent literature arefound in U.S. Pat. Nos. 3,282,875; 4,138,426; 4,538,545; 4,940,525;4,982,009; 5,196,569; 5,637,748; 5,866,711; and 5,969,067.

Preferred embodiments of functional vinyl ethers include:

-   CF₂═CF—O—CF₂—CF(CF₃)O—CF₂CF₂—SO₂F    (perfluoro-3,6-dioxa-4-methyl-7-octenesulfonyl fluoride), its    corresponding acid, salts, or amides;-   CF₂═CF—O—CF₂—CF(CF₃)O—CF₂CF₂—COOR″ (ester, preferably methyl ester,    of perfluoro-4,7-dioxa-5-methyl-8-nonenoic acid), its corresponding    acid, salts, or amides;-   CF₂═CF—O—CF₂CF₂—SO₂F (perfluoro-3-oxa-4-pentenesulfonyl fluoride),    its corresponding acid, salts, or amides;-   CF₂═CF—O—CF₂CF₂—COOR″ (ester, preferably methyl ester, of    perfluoro-4-oxa-5-hexenoic acid), its corresponding acid, salts, or    amides;-   CF₂═CF—O—CF₂—CF(CF₃)—CF₂CF₂—CH₂OH    (9,9-dihydro-9-hydroxy-perfluoro(3,6-dioxa-5-methyl-1-nonene));-   CF₂═CF—O—CF₂CF₂CF₂—CH₂OH    (7,7-Dihydro-7-hydroxy-perfluoro(3-oxa-1-heptene));-   CF₂═CF—O—CF₂—CF(CF₃)—CF₂CF₂—CH2OP(O)(OH)₂    (9-phosphono-9,9-dihydro-perfluoro(3,6-dioxa-5-methyl-1-nonene));-   CF₂═CF—O—CF₂—CF(CF₃)—CF₂CF₂CN    (perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene).

R further represents: (C) alkenyl. Alkenyl means an alkyl groupcontaining at least one site of olefinic unsaturation. It is preferredthat there be a single site of olefinic unsaturation and preferably thatthe olefinic unsaturation be a terminal vinyl group. Alkyl meanshydrocarbon group, which may be substituted with halogen and, if sosubstituted, preferably the halogen is fluorine or chlorine, preferablyalkyl is fluoroalkyl, and more preferably is perfluoroalkyl. Alkyl maybe linear or branched, or cyclic. Preferably, alkyl is linear alkyl. Thealkyl group may contain one or more ether linkages. Preferably, thealkyl group has 1 to 20 carbon atoms. These fluorovinyl ethers arepreferably trifluorvinyl alkenyl vinyl ethers. Preferred fluorovinylethers are perfluoro(alkenyl vinyl ethers). Examples are perfluoro(allylvinyl ether), perfluoro(3-butenyl vinyl ether);1,1-dihydro-2,2,3,4,4-pentafluoro-3-butenyl trifluorovinyl ether, and1,1-dihydroperfluoro-4-pentenyl trifluoro vinyl ether (U.S. Pat. Nos.4,897,457 and 5,260,492). This class of vinyl ethers can react accordingto this invention to give disulfonic acids and sulfonates because boththe vinyl ether portion of the molecule and the alkenyl group react withsulfite. Members of this class of fluorovinyl ethers are referred toherein as fluoro(alkenyl vinyl ethers).

In each of the classes of R described above, R is said to be fluorinatedif at least one of the monovalent atoms bonded to carbon atom in R is afluorine atom. R is said to be perfluorinated if all of the monovalentatoms bonded to carbon atom in R are fluorine atoms.

The discovery that fluorovinyl ethers can react with sulfite to givehydrofluoroalkanesulfonates makes higher molecular weight, and higherboiling, hydrofluoroalkanesulfonic acids more readily available as wellas the corresponding sulfonates. PAVEs are widely used in fluoropolymersof the “PFA” type and commercial facilities for their large scaleproduction are in place. In contrast, higher fluoroolefins, that isfluoroolefins beyond hexafluoropropylene, and especially beyondoctafluorobutylene, are not used in fluoropolymers in significantamount, so their availability is limited. Certain functional vinylethers and fluoro(alkenyl vinyl ethers) are also the basis of commercialfluoropolymers.

The term sulfite (SO₃ ⁼) is used herein with the understanding that inaqueous solution this species is in equilibrium with bisulfite (HSO₃ ⁻).This equilibrium may also include sulfurous acid (H₂SO₃) and sulfurdioxide (SO₂). The ratio of sulfite to bisulfite is a function of the pHof the solution. SO₃ ⁼/HSO₃ ⁻ forms a buffer that with proper controlcan effectively buffer the reaction according to this invention withoutthe introduction of extraneous materials such as borax and phosphate. Itis advantageous to avoid extraneous materials because these can be thesource of impurities in the product and, in addition, add to the cost ofingredients, increase the variety of chemicals in the waste product,thus increasing the difficulty and cost of disposal or recovery.

The optimum pH range for the formation of hydrofluoroalkanesulfonicacids according to this invention is about 4 to 12, preferably about 5to 11, more preferably about 5 to 10, and most preferably about 5 to 9.Optimum pH can be attained by adding a sulfite source such as sulfurdioxide (SO₂), sulfurous acid, bisulfite, and/or sulfite to water, andadjusting the pH by further addition of a reagent that does notintroduce extraneous materials into the reaction. By extraneous materialis meant material that is unrelated to the necessary ingredients of thereaction according to this invention. Necessary ingredients are water,sulfite or sulfuric acid. Ingredients that are fugitive in the sense ofbeing easily removed without contamination of the product or residue,such as carbonate, bicarbonate, and or carbon dioxide, are notconsidered extraneous materials.

Such non-extraneous materials include hydroxide, carbon dioxide (CO₂),bicarbonate, carbonate, sulfuric acid, bisulfate, and sulfate, andsulfurous acid, bisulfite, and sulfite. If the initially made solutionhas too high a pH, one or more of the acidic types of materials listedabove, e.g. SO₂, sulfuric acid, bisulfate, or CO₂ are added. If theinitially made solution has too low a pH, one or more of the basic typesof materials listed above, e.g. hydroxide, sulfite, or carbonate, areadded.

CO₂ is a particularly effective reagent. When present, it acts to bufferthe reaction and suppress all but the desired product. It is believedthat it does this by reacting with hydroxyl (OH⁻) ion formed in thereaction of sulfite, the effective reactant, with the fluoro(alkyl vinylether), as shown in equation (3) below:R—O—CF═CF₂+SO₃ ⁼+H₂O->R—O—CHF—CF₂SO₃ ⁻+OH⁻  (3)One mole of H₂OO₃, which is in equilibrium with CO₂ in water, reactswith two OH⁻ to form carbonate (CO₃ ⁼), thereby suppressing the reactionof OH⁻ with vinyl ether to form the acid. Therefore, one mole of CO₂will neutralize OH⁻ from the reaction of two moles of vinyl ether withSO₃ ⁼. Preferably, the mole ratio of vinyl ether to CO₂ should be closeto the stoichiometric 66:33 (vinyl ether/CO₂), such as in the rangeabout 50:50 to about 75:25, more preferably about 60:40 to 70:30, andmost preferably about 64:36 to 68:32.

Alternatively, fluorovinyl ether and CO₂ may be added in separatestreams in the desired ratio, or the CO₂ addition may be controlled bymeans that monitor the reaction solution pH and adjust CO₂ addition rateto maintain pH in the desired range.

It is preferred that, for reagents that are ionic, those with alkalimetal salts cations be used, preferably the sodium or potassium ion,more preferably the potassium ion. As discussed below, the product ofthe process will be the hydrofluoroalkanesulfonate salt of the metal ionor ions used in the synthesis.

It is not desirable to have radical initiators, particularly radicalinitiators capable of initiating the polymerization of fluorovinyl etherpresent in the reaction mixture and preferably are not employed in theprocess of the invention. Furthermore, oxygen preferably should beexcluded from the reaction vessel, since oxygen is capable of reactingwith fluorovinyl ether and may lead to oligomerization. Oxygen can thuscause side reactions that compete with formation ofhydrofluoroalkanesulfonic acid, reducing yield and creating uselessbyproducts that can foul the reactor and cause plugging of lines. Inaddition, oxygen reacts with sulfite to form sulfate. Since the sulfiteconcentration is important to controlling the pH of the reaction, suchoxidation by oxygen is undesirable.

In the making the hydrofluoroalkanesulfonate according to thisinvention, a suitable vessel, preferably of stainless steel or othercorrosion resistant metal, is charged with aqueous sulfite solution. Thesolution may be prepared outside the vessel, or made in situ, bycharging water and dry ingredients. It is preferred that the water bedeionized and oxygen-free. If it is desired to avoid handling dryingredients, the sulfite solution may be prepared by adding sulfurdioxide (SO₂) to aqueous caustic, preferably sodium or potassiumhydroxide. pH of the solution should be adjusted to about 4-12. If asulfite salt, such as sodium or potassium sulfite is the sulfite source,sulfuric acid is a convenient acid for pH adjustment.

After the aqueous sulfite is charged, the vessel is cooled to about 0°C. to −40° C., evacuated and then charged with nitrogen or other inertgas at least once and preferably 2 to 3 times to eliminate oxygen. Thevessel is evacuated and then charged with the fluorovinyl ether, closed,and heating is begun. Temperature is raised to about 125° C. and heldthere with stirring, shaking, or other means of agitating the vesselcontents for about 2 to 12 hours. At the end of the reaction time, thevessel is cooled to room temperature, vented, and the contentsdischarged.

The contents may be concentrated by removal of water, preferably atreduced pressure, preferably in a rotary evaporator. More preferably,water-removal in the rotary evaporator is not carried to the point ofdryness. Rather water is further removed by freeze drying. Freeze dryingresults in a finely divided, easily handled, low moisture solid.Otherwise, the resulting solids tend to be hard and lumpy. The productfrom the freeze drier preferably contains less than about 5 wt % water,more preferably contains less than about 1 wt % water, and mostpreferably contains less than about 0.5 wt % water.

Also preferable, is the removal of water by spray-drying the aqueousreaction product.

After water-removal, the solid (crude product) can be further purifiedby stirring in reagent grade acetone for several hours at roomtemperature. The product hydrofluoroalkanesulfonate dissolves inacetone, the inorganic salts, such as residual sulfite salts, do not.Filtration of the acetone solution removes undissolved impurities. Theacetone solution is then subject to vacuum to remove acetone. Theresulting solids, purified hydrofluoroalkanesulfonate salt, can befurther dried at low pressure, about 1-20 Pa, at room temperature toremove remaining acetone.

It has been found that on cooling the reactor contents from the reactionof PMVE or PEVE, that the product hydrofluoroalkanesulfonate saltprecipitates in high purity (greater than about 98%), leaving littleproduct in the liquid phase. The carboxylic acid salt arising from thereaction shown in equation (2) is more soluble and remains in the liquidphase. When a sufficiently quantitative precipitation of the desiredproduct occurs (this sufficiency will depend on the process economics,including the scale of the process), freeze drying or spray drying ofthe crude product and acetone purification are preferably omitted.

The product will be the hydrofluoroalkanesulfonate salt of the metal ionor ions used in the synthesis. For example, if potassium sulfite is thesource of sulfite, potassium hydrofluoroalkanesulfonate will theproduct, i.e. potassium ion will be the cation. Potassium is a preferredcation for the hydrofluoroalkanesulfonate salt. If another cation formof the hydrofluoroalkanesulfonate is desired, such as another metal ion,this can be done using ion-exchange or metathetical methods known in theart. The salt can be converted to the acid, i.e. proton (hydrogen ion)is the cation, by reaction with an acid such as by contact with strongacid ion exchange resin, for example, resin made by sulfonatingcrosslinked polystyrene. For convenience, hydrofluoroalkanesulfonate andthe corresponding hydrofluoroalkanesulfonic acid can be represented as ahydrofluoroalkanesulfonate of the formula R—O—CFH—CF₂—SO₃M, where R isselected from the group consisting of alkyl groups, functionalized alkylgroups, and alkenyl groups, and M is a proton, in which case themolecule is the hydrofluoroalkanesulfonic acid, or other cation, inwhich case the salt is meant.

A preferred method of acidification is treatment with oleum. This isdone after water is removed, but the acetone purification step is notnecessary. Acidification may be done on the crude product. It ispreferred that the crude product be freeze dried to remove water.

The term “oleum” means H₂SO₄ containing sulfur trioxide (SO₃),preferably in the range of about 1 to 15 wt %. The oleum is preferablyused in a weight ratio of at least about 1 part oleum per part driedproduct. By using oleum, rather than concentrated sulfuric acid, whichgenerally contains from 2-5 wt % water, formation ofhydrofluoroalkanesulfonic acid hydrate is avoided. The acid hydrates areoften waxy solids at room temperature. They can solidify in thecondenser during distillation unless the temperature of the condensercoolant is controlled, which is a burdensome requirement.

Commercially available oleum may have too high an SO₃ content. If so,the SO₃ concentration can be reduced by mixing the commercial oleum withsulfuric acid. The sulfuric acid addition dilutes the commercial oleum,and water in the sulfuric acid reacts with some of the SO₃ to formsulfuric acid. The result is oleum of lower SO₃ concentration.

Addition of the oleum gives a slurry, which, on heating in the still,may form a solution, depending on the particular sulfonic acid.

A large excess of oleum is not desirable. It can lead to reduced yieldsof the sulfonic acid and formation of lower boiling product, believed tobe sulfonic acid ester. In the process there should be a small amount,preferably no more than about 5 wt %, more preferably no more than about3 wt %, most preferably no more than about 1 wt % of low boilingmaterial coming off the distillation before the desired sulfonic acidproduct. This ensures that no hydrate remains to foul the still. Lowboiling material in excess of this is an indication that too much oleumis being used, and the amount should be reduced.

In accordance with a preferred form of the invention which is usefulwhen water is removed by methods other then precipitation in highpurity, the resulting solid is preferably converted to the acid form by“directly treating” the solid with oleum. The term “directly treating”with oleum means that no intervening extraction steps are used and theoleum mixed or contacted with the product for treatment. The oleummixture is then heated to boiling and the product acid distilled off. Ifthe acid is found to be in hydrate form, that is combined with water,stronger oleum or more complete water removal from the product isdesirable to avoid additional process steps, such as treatment of theacid hydrate with thionyl chloride to make the unhydrated acid.

Preferred classes of hydrofluoroalkanesulfonate according to thisinvention are:

-   MO₃S—CF₂—CHF—(OCF₂CF(CF₃))_(n)(O)_(p)(CF₂)_(m)—Z, where M is a    cation, where p is 0 or 1, m is 0 to 10 and n is 1 to 20, provided    that when m is 0, p is 0, and further provided that when m is    greater than 0, p is 1, and Z is a functional group such as —CH₂OH,    carboxyl (—COO⁻) including carboxylic ester, amide, acid, or salt;    sulfonate (—SO₃ ⁻) including sulfonyl halide, preferably fluoride,    sulfonic acid, sulfonamide, or sulfonate salt; phosphonate    (—O—P(O)O₂ ⁻), including phosphonic acid, acid halide, or salt;    glycidyl; cyanide (—CN); cyanate, and carbamate.-   Hydrofluoroalkanesulfonates of the formula MO₃S—CF₂—CHF—O—Y—CF₂—Z,    where M is a cation, where Y is alkylene, preferably fluoroalkylene,    and more preferably perfluoroalkylene and may be cyclic and may    include one or more ether oxygens, and is most preferably CF₂, and Z    is a functional group such as —CH₂OH, carboxyl (—COO⁻) including    carboxylic ester, amide, acid, or salt; sulfonate (—SO₃ ⁻) including    sulfonyl halide, preferably fluoride, sulfonic acid, sulfonamide, or    sulfonate salt; phosphonate (—O—P(O)O₂), including phosphonic acid,    acid halide, or salt; glycidyl; cyanide (—CN); cyanate, and    carbamate.-   MO₃S—CF₂—CHF—O—CF₂—CF(CF₃)O—CF₂CF₂—SO₂M¹, where M is a cation and M¹    is selected from the group consisting of OH, NR¹R² where R¹ and R²    are independently hydrogen or alkyl, and OX, where X is a cation.-   MO₃S—CF₂—CHF—O—CF₂—CF(CF₃)O—CF₂CF₂—COM¹, where M is a cation and-   M¹ is selected from the group consisting of OH, NR¹R² where R¹ and    R² are independently hydrogen or alkyl, and OX, where X is a cation.-   MO₃S—CF₂—CHF—O—CF₂CF₂—SO₂M¹, where M is a cation and M¹ is selected    from the group consisting of OH, NR¹R² where R¹ and R² are    independently hydrogen or alkyl, and OX, where X is a cation.-   MO₃S—CF₂—CHF—O—CF₂CF₂—COM¹, where M is a cation and M¹ is selected    from the group consisting of OH, NR¹R² where R¹ and R² are    independently hydrogen or alkyl, and OX, where X is a cation.-   MO₃S—CF₂—CHF—O—CF₂—CF(CF₃)O—CF₂CF₂CH₂OH. This is derived from    MO₃S—CF₂—CHF—O—CF₂—CF(CF₃)O—CF₂CF₂CN.-   MO₃S—CF₂—CHF—O—CF₂—CF(CF₃)O—CF₂CF₂CH₂OP(O)(OM)₂.-   MO₃S—CF₂—CHF—O—CR₂(CF₂)_(n)CFHCF₂—SO₃M.    For hydrofluoroalkanesulfonates with more than one ionic group, the    cations need not be identical.

The process as described above may be carried out as a batch process.The process according to this invention may also be run continuously,with continuous or periodic drawing off of the liquid contents of thereactor and continuous or periodic replenishment of reactants.

Salts of the above described hydrofluoroalkanesulfonates useful asphotoacid generators or ionic liquids have cations selected from theclass, organic onium ions. These include sulfonium and iodonium, such astriphenyl sulfonium and diphenyl iodonium, preferred for photoacidgenerators, as well as ammonium, phosphonium, bromonium, chloronium andarsonium, among others.

In making the salts starting with the acid, R—O—CXH—CX₂—SO₃H, the acidmay be reacted with a silver salt, e.g., silver carbonate, to form thesilver salt of the sulfonic acid, R—O—CXH—CX₂—SO₃Ag. This silver salt isthen reacted with, for example, [(R¹)(R²)(R³)S⁺]X⁻ or [(R⁴)(R⁵)I⁺]X⁻(where X═Cl, Br, or I) to form insoluble AgX and the desired oniumcation. Y⁺RfSO₃ ⁻.

A preferred method is direct reaction of the potassium salt,R—O—CXH—CX₂—SO₃K, with, for example, (R¹)(R²)(R³)S⁺X— or (R⁴)(R⁵)I⁺X⁻(X═Br, Cl, I) to form insoluble MX and the desired sulfonium or iodoniumsalt, R—O—CXH—CX₂—SO₃M. This method obviates the need for forming theacid, and can give materials of high purity, e.g., less than 10 ppm ofmetals that might be deleterious to photolithography processes.

In selected embodiments of this invention, M is triphenylsulfonium ortris(4-t-butylphenyl)sulfonium.

For convenience, is referred to herein as sulfonium or iodonium. In thestructures above, R¹, R², R³, R⁴, and R⁵ each independently represent analkyl group, a monocyclic or bicyclic alkyl group, a phenyl group, anaphthyl group, an anthryl group, a peryl group, a pyryl group, athienyl group, an aralkyl group, or an arylcarbonylmethylene group; orany two of R¹, R², and R³ or R⁴ and R⁵ together represent an alkylene oran oxyalkylene which forms a five- or six-membered ring together withthe interposing sulfur or iodine, said ring being optionally condensedwith aryl groups, one or more hydrogen atoms of R¹, R², R³, R⁴, and R⁵being optionally substituted by one or more groups selected from thegroup consisting of a halogen atom, an alkyl group, a cyclic alkylgroup, an alkoxy group, a cyclic alkoxy group, a dialkylamino group, adicyclic dialkylamino group, a hydroxyl group, a cyano group, a nitrogroup, an aryl group, an aryloxy group, an arylthio group, and groups offormulas I to V:

wherein R⁶ and R⁷ each independently represent a hydrogen atom, an alkylgroup, which may be substituted by one or more halogen atoms, or acyclic alkyl group, which may be substituted by one or more halogenatoms, or R⁶ and R⁷ together can represent an alkylene group to form aring, R⁸ represents an alkyl group, a cyclic alkyl group, or an aralkylgroup, or R⁶ and R⁸ together represent an alkylene group which forms aring together with the interposing —C—O— group, the carbon atom in thering being optionally substituted by an oxygen atom, R⁹ represents analkyl group or a cyclic alkyl group, one or two carbon atoms in thealkyl group or the cyclic alkyl group being optionally substituted by anoxygen atom, an aryl group, or an aralkyl group, R¹⁰ and R¹¹ eachindependently represent a hydrogen atom, an alkyl group or a cyclicalkyl group, R¹² represents an alkyl group, a cyclic alkyl group, anaryl group, or an aralkyl group, and R¹³ represents an alkyl group, acyclic alkyl group, an aryl group, and aralkyl group, the group—Si(R¹²)₂R¹³, or the group —O—Si(R¹²)₂R¹³

The binders useful as photoresist resins for this invention comprise anypolymer that has the transparency properties suitable for use inmicrolithography. It is contemplated that binders suitable for thepresent invention may include those polymers that are typicallyincorporated into chemically amplified 248 (deep UV) and 193 nmphotoresists for imaging at longer wavelengths. A typical 248 nmphotoresist binder is based on polymers of para-hydroxystyrene. Otherexamples of suitable 248 nm photoresist binders can be found in thereference Introduction to Microlithography, Second Edition by L. F.Thompson, C. G. Willson, and M. J. Bowden, American Chemical Society,Washington, D.C., 1994, chapter 3. Binders useful for 193 nmphotoresists include cycloolefin-maleic anhydride alternating copolymers[such as those disclosed in F. M. Houlihan et al., Macromolecules, 30,pages 6517-6534 (1997); T. Wallow et al., Proc. SPIE, 2724, 355; and F.M. Houlihan et al., Journal of Photopolymer Science and Technology, 10,511 (1997)], polymers of functionalized norbornene-type monomersprepared by metal-catalyzed vinyl addition polymerization orring-opening metathesis polymerization [such as those disclosed in U.Okoroanyanwu et al. J. Mol. Cat. A: Chemical 133, 93 (1998), and PCT WO97/33198], and acrylate copolymers [such as those described in U.S. Pat.No. 5,372,912]. Photoresist binders that are suitable for use with thisinvention also include those which are transparent at wavelengths below248 and 193 nm such as those polymers containing fluoroalcoholfunctional groups [such as those disclosed in K. J. Pryzbilla et al.Proc. SPIE 1672, 9 (1992), and H. Ito et al. Polymn. Mater. Sci. Eng.77, 449 (1997)].

Typical examples of polymers that are also useful are those that havebeen developed for use in chemically amplified photoresists which areimaged at an irradiation wavelength of 157 nm. Examples of such polymersare fluoropolymers and fluoropolymers containing fluoroalcoholfunctional groups. Suitable examples have been disclosed in WO 00/17712and WO 00/25178.

The quantity of polymeric binder in the photoresist composition may bein the amount of about 50 to about 99.5 weight % based on the weight ofthe total photoresist composition (solids).

A photoresist composition in accordance with the invention contains acombination of polymeric binder and photoactive component, i.e., organiconium hydrofluoroalkanesulfonate. The photoactive compound may bepresent in the amount of about 0.5 to about 10% by weight typicallyabout 1 to about 5% by weight, based on the total dry weight ofphotoresist composition.

Various dissolution inhibitors can be utilized in the photoresistcomposition in accordance with the invention. Ideally, dissolutioninhibitors (DIs) for the far and extreme UV photoresists (e.g., 193 nmphotoresists) are selected to satisfy multiple needs includingdissolution inhibition, plasma etch resistance, and adhesion behavior ofphotoresist compositions comprising a given DI additive. Typically, adissolution inhibitor is included in a photoresist composition to assistin the development process. A good dissolution inhibitor will inhibitthe unexposed areas of the photoresist layer from dissolving during thedevelopment step in a positive working system. A useful dissolutioninhibitor may also function as a plasticizer which function provides aless brittle photoresist layer that will resist cracking. These featuresare intended to improve contrast, plasma etch resistance, and adhesionbehavior of photoresist compositions.

Some dissolution inhibiting compounds may also serve as plasticizers inphotoresist compositions.

A variety of bile-salt esters (i.e., cholate esters) are particularlyuseful as dissolution inhibitors in the compositions of this invention.Bile-salt esters are known to be effective dissolution inhibitors fordeep UV photoresists, beginning with work by Reichmanis et al. in 1983.(E. Reichmanis et al., “The Effect of Substituents on thePhotosensitivity of 2-Nitrobenzyl Ester Deep UV Resists”, J.Electrochem. Soc. 1983, 130, 1433-1437.) Bile-salt esters areparticularly attractive choices as dissolution inhibitors for severalreasons, including their availability from natural sources, theirpossessing a high alicyclic carbon content, and particularly for theirbeing transparent in the deep and vacuum UV region, (which essentiallyis also the far and extreme UV region), of the electromagnetic spectrum(e.g., typically they are highly transparent at 193 nm). Furthermore,the bile-salt esters are also attractive dissolution inhibitor choicessince they may be designed to have widely ranging hydrophobic tohydrophilic compatibilities depending upon hydroxyl substitution andfunctionalization.

Representative bile-acids and bile-acid derivatives that are suitable asdissolution inhibitors for this invention include, but are not limitedto, those illustrated below, which are as follows: cholic acid (IV),deoxycholic acid (V), lithocholic acid (VI), t-butyl deoxycholate (VII),t-butyl lithocholate (VIII), and t-butyl-3-α-acetyl lithocholate (IX).Bile-acid esters, including compounds VII-IX, are preferred dissolutioninhibitors in this invention.

The quantity of dissolution inhibitor in the photoresist composition mayrange from about 0.5 to about 50 wt % based on the total weight of thesolids in the photoresist composition.

The compositions of this invention can contain optional additionalcomponents. Examples of additional components which can be addedinclude, but are not limited to, resolution enhancers, adhesionpromoters, residue reducers, coating aids, plasticizers, and T_(g)(glass transition temperature) modifiers. Crosslinking agents may alsobe present in negative-working photoresist compositions. Some typicalcrosslinking agents include bis-azides, such as, 4,4′-diazidodiphenylsulfide and 3,3′-diazidodiphenyl sulfone. Typically, a negative workingcomposition containing at least one crosslinking agent also containssuitable functionality (e.g., unsaturated C═C bonds) that can react withthe reactive species (e.g., nitrenes) that are generated upon exposureto UV to produce crosslinked polymers that are not soluble, dispersed,or substantially swollen in developer solution.

The photoresist composition can include an amount of solvent, typicallyan organic solvent such as cyclohexanone. The solvent is usually used inan amount sufficient to dissolve the binder and the photoactivecomponent. A specific solvent found to be useful is cyclohexanone.

The process for forming a photoresist image on a substrate comprises, inorder:

(A) imagewise exposing a photoresist layer to form imaged and non-imagedareas, wherein the photoresist layer is prepared from a photoresistcomposition comprising:

(a) a polymeric binder; and

(b) a photoactive component selected from photoacid generators, Y⁺R_(f)SO₃ ⁻, as described above;

(B) developing the exposed photoresist layer having imaged andnon-imaged areas to form the relief image on the substrate.

The photoresist layer is prepared by applying a photoresist compositiononto a substrate and drying to remove the solvent. The photoresist layeris, typically, applied by spin coating onto a substrate, typically asilicon wafer having a primer applied thereon. The so formed photoresistlayer is sensitive in the ultraviolet region of the electromagneticspectrum and especially to those wavelengths ≦365 nm. Imagewise exposureof the photoresist compositions of this invention can be done at manydifferent UV wavelengths including, but not limited to, 365 nm, 248 nm,193 nm, 157 nm, and lower wavelengths. Imagewise exposure is preferablydone with ultraviolet light of 248 nm, 193 nm, 157 nm, or lowerwavelengths, preferably it is done with ultraviolet light of 193 nm, 157nm, or lower wavelengths, and most preferably, it is done withultraviolet light of 157 nm or lower wavelengths. Imagewise exposure caneither be done digitally with a laser or equivalent device ornon-digitally with use of a photomask. Digital imaging with a laser ispreferred. Suitable laser devices for digital imaging of thecompositions of this invention include, but are not limited to, anargon-fluorine excimer laser with UV output at 193 nm, akrypton-fluorine excimer laser with UV output at 248 nm, and a fluorine(F₂) laser with output at 157 nm. Since, as discussed supra, use of UVlight of lower wavelength for imagewise exposure corresponds to higherresolution (lower resolution limit), the use of a lower wavelength(e.g., 193 nm or 157 m or lower) is generally preferred over use of ahigher wavelength (e.g., 248 nm or higher). After exposure, the wafer isusually baked to increase or decrease the ability of exposed areas ofthe photoresist to be removed in developer. The photoresist compositionsof this invention must contain sufficient functionality for developmentfollowing imagewise exposure to UV light. Preferably, the functionalityis an acid or protected acid such that aqueous development is possibleusing a basic developer such as sodium hydroxide solution, potassiumhydroxide solution, or ammonium hydroxide solution, such astetramethylammonium hydroxide.

When an aqueous processible photoresist is coated or otherwise appliedto a substrate and imagewise exposed to UV light, development of thephotoresist composition may require that the binder material shouldcontain sufficient acid groups (e.g., fluoroalcohol groups) and/orprotected acid groups that are at least partially deprotected uponexposure to render the photoresist (or other photoimageable coatingcomposition) processible in aqueous alkaline developer. In case of apositive-working photoresist layer, the photoresist layer will beremoved during development in portions which are exposed to UV radiationbut will be substantially unaffected in unexposed portions duringdevelopment by aqueous alkaline liquids such as wholly aqueous solutionscontaining 0.262 N tetramethylammonium hydroxide (with development at25° C. usually for less than or equal to 120 seconds). In case of anegative-working photoresist layer, the photoresist layer will beremoved during development in portions which are unexposed to UVradiation but will be substantially unaffected in exposed portionsduring development using either a critical fluid or an organic solvent.

A critical fluid, as used herein, is one or more substances heated to atemperature near or above its critical temperature and compressed to apressure near or above its critical pressure. Critical fluids in thisinvention are at least at a temperature that is higher than 15° C. belowthe critical temperature of the fluid and are at least at a pressurehigher than 5 atmospheres (500 kPa) below the critical pressure of thefluid. Carbon dioxide may be used for the critical fluid in the presentinvention. Various organic solvents can also be used as developer inthis invention. These include, but are not limited to, halogenatedsolvents and non-halogenated solvents. Halogenated solvents are typicaland fluorinated solvents are more typical.

The substrate employed in this invention can be any material used insemiconductor manufacture, for example, a wafer usually made fromsilicon, silicon oxide, silicon nitride and the like. Usually, a primeris applied to the silicon wafer. A typical primer composition ishexamethyldisilazane.

EXAMPLES Glossary Analytical/Measurements

-   -   bs broad singlet    -   δ NMR chemical shift measured in the indicated solvent    -   g gram    -   NMR Nuclear Magnetic Resonance    -   ¹H NMR Proton NMR    -   ¹⁹F NMR Fluorine-19 NMR    -   s singlet    -   sec. second(s)    -   m multiplet    -   mL milliliter(s)    -   mm millimeter(s)    -   T_(g) Glass Transition Temperature    -   M_(n) Number-average molecular weight of a given polymer    -   M_(w) Weight-average molecular weight of a given polymer    -   P=M_(w)/M_(n) Polydispersity of a given polymer    -   Absorption coefficient AC=A/b, where A, absorbance, =Log₁₀ (1/T)        and b=film thickness in microns, where T=transmittance as        defined below.    -   Transmittance Transmittance, T, =ratio of the radiant power        transmitted by a sample to the radiant power incident on the        sample and is measured for a specified wavelength λ (e.g., nm).

Chemicals/Monomers

-   -   HAdA Hydroxyadamantyl acrylate (2-Propenoic acid,        3-hydroxytricyclo[3.3.1.13, 7]dec-1-yl ester) [CAS registry        number 216581-76-9](Idemitsu Chemical USA, Southfield, Mich.)    -   MAdA 2-Methyl-2-adamantyl acrylate (2-propenoic acid,        2-methyltricyclo[3.3.1.13, 7]dec-2-yl ester) [CAS Registry        number 249562-06-9](Idemitsu Chemical USA, Southfield, Mich.)    -   PinAc 2-Propenoic acid, 2-hydroxy-1,1,2-trimethylpropyl ester        [CAS Reg number 97325-36-5]    -   TFE Tetrafluoroethylene E.I. du Pont de Nemours and Company,        Wilmington, Del.    -   THF Tetrahydrofuran Sigma-Aldrich Chemical Co., St. Louis, Mo.    -   NB—F—OH X═OCH₂C(CF₃)₂OH

NB—F—OH was prepared as described by Feiring and Feldman, PCT Int. Appl.WO 2000067072 (Nov. 9, 2000).

Ultraviolet

-   -   Extreme UV Region of the electromagnetic spectrum in the        ultraviolet that ranges from 10 nanometers to 200 nanometers    -   Far UV Region of the electromagnetic spectrum in the ultraviolet        that ranges from 200 nanometers to 300 nanometers    -   UV Ultraviolet region of the electromagnetic spectrum which        ranges from 10 nanometers to 390 nanometers    -   Near UV Region of the electromagnetic spectrum in the        ultraviolet that ranges from 300 nanometers to 390 nanometers

Unless otherwise specified, all temperatures are in degrees Celsius, allmass measurements are in grams, and all percentages are weightpercentages.

Unless otherwise indicated, n, appearing within structure(s) given inthe examples, represents the number of repeat units in the polymer.Throughout the specification, p, appearing within structure(s),represents the number of repeat units in the polymer.

Glass transition temperatures (T_(g)) were determined by DSC(differential scanning calorimetry) using a heating rate of 20° C./min,data is reported from the second heat. The DSC unit used is a ModelDSC2910 made by TA Instruments, Wilmington, Del.

The term “clearing dose” indicates the minimum exposure energy density(e.g., in units of mJ/cm²) to enable a given photoresist film, followingexposure, to undergo development.

Unless otherwise indicated, all reagents were obtained fromSigma-Aldrich Co. (St. Louis, Mo.).

Example 1 Synthesis of Potassium1,1,2-Trifluoro-2-(trifluoromethoxy)ethanesulfonate (TTES-K) and1,1,2-Trifluoro-2-(trifluoromethoxy)ethanesulfonic acid

This example demonstrates the reaction of perfluoro(methyl vinyl ether)(PMVE) according to this invention. A 400 ml Hastelloy® C276 reactionvessel is charged with a solution of 11.4 g potassium bisulfite hydrate(KHSO₃.H₂O, 95%, Aldrich, 0.07 mol), 44.5 g potassium metabisulfite(K₂S₂O₅, 99%, Mallinckrodt, 0.20 mol) and 200 ml of deionized water. ThepH of this solution is 5.8. The vessel is cooled to −35° C., evacuatedto −3 psig (80.6 kPa), and purged with nitrogen. The evacuate/purgecycle is repeated two more times. To the vessel is then added 60 gperfluoro(methyl vinyl ether) (PMVE, 0.36 mol). The vessel is heated to125° C. at which time the internal pressure is 571 psig (4040 kPa). Thereaction temperature is maintained at 125° C. for 4 hr. The pressuredrops to 33 psig (330 kPa) at which point the vessel is vented andcooled to 25° C. The reaction product is a clear light yellow reactionsolution of pH 7.0, and a precipitate

The crude reaction product is placed in a freeze dryer (VirtisFreezemobile 35xl) for 72 hr to reduce the water content toapproximately 0.5 wt. % (117 g). The theoretical mass of total solids isapproximately 119 g. The crude product is stirred with 800 ml of reagentgrade acetone for 4 hr at 25° C. The product dissolves, the undissolvedinorganic salts are removed by filtration through a fritted glassfunnel. The acetone is removed in vacuo and the remaining solid is driedat 30 milliTorr (4 Pa) at 25° C. for 3 hours to remove residual acetoneaffording 86.7 g (84% yield) of white solid identified (see below) aspotassium 1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate (TTES-K).

¹⁹F NMR (D₂O) δ−59.9d, ³J_(FH)=4 Hz, 3F); −119.6, −120.2 (subsplit ABq,J=260 Hz, 2F); −144.9 (dm, ²J_(FH)=53 Hz, 1F)

¹H NMR (D₂O) δ 6.6 (dm, ²J_(FH)=53 Hz, 1H).

% Water by Karl-Fisher titration: 71 ppm.

Analysis calculated for C₃HF₆SO₄K: C, 12.6: H, 0.4: N, 0.0; Found: C,12.6: H, 0.0: N, 0.1.

Melting point (DSC) 257° C.

TGA (air): 10% weight loss at 343° C., 50% weight loss at 358° C.

TGA (nitrogen): 10% weight loss at 341° C., 50% weight loss at 375° C.

A 100 ml round bottom flask with a sidearm is equipped with a digitalthermometer and a magnetic stirbar and placed in an ice bath underpositive nitrogen pressure. To the flask is added 60 g crude TTES-K fromthe previous step along with 35 g of concentrated sulfuric acid (EMScience, 95-98%) and 95 g oleum (Acros, 20 wt % SO3) while stirring.This amount of oleum is chosen so that the SO3 reacts with and removesthe water in the sulfuric acid as well as in the crude TTES-K whilestill being present in slight excess. The mixing causes a small exothermwhich is controlled by the ice bath. Once the exotherm is over, adistillation head with a water condenser is placed on the flask and itis heated under nitrogen behind a safety shield. The pressure is slowlyreduced using a PTFE membrane vacuum pump (Buchi V-500) in steps of 100Torr (13 kPa) in order to avoid foaming. A dry-ice trap is also placedbetween the distillation apparatus and the pump to collect any excessSO₃. The flask is heated and the pressure is held at 20-30 Torr (2.7−4.0kPa). The flask contents begin to reflux and then distill. A forerun oflower-boiling impurity (approximately 2 g) is obtained before collecting30 g of the colorless liquid, which by NMR analysis is found to have aspectrum consistent with that of the expected acid,1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonic acid.

Example 2 Synthesis of Potassium1,1,2-Trifluoro-2-(trifluoromethoxy)ethanesulfonate (TTES-K)

A 1-gallon Hastelloy C276 reaction vessel is charged with a solution of114 g potassium sulfite hydrate (KHSO₃.H2O, 95%, Aldrich, 0.72 mol), 440g potassium metabisulfite (K₂S₂O₅, 99%, Mallinckrodt, 1.98 mol) and 2000mL of deionized water. The pH of this solution is 5.8. The vessel iscooled to −35° C., evacuated to −3 psig (81 kPa), and purged withnitrogen. This evacuate/purge cycle is repeated two more times. 600 gperfluoro(methyl vinyl ether) (PMVE, 3.61 mol) is added to the vessel,which is heated to 125° C. at which time the internal pressure is 462psig (3290 kPa). The reaction temperature is maintained at 125° C. for 6hr. The pressure drops to 25 psig (275 kPa) at which point the vessel isvented and cooled to 25° C. Once cooled, a white crystalline precipitateof the forms, leaving clear colorless liquid above it (pH=7). ¹⁹F NMR ofthe white solid shows it to be the desired product in high purity(>98%). ¹⁹F NMR of the liquid shows a small but detectable amount of thehydration product of Equation (3), above.

The liquid and precipitate are slurried and suction filtered through afritted glass funnel for 6 hr to remove most of the water. The wet cakeis then dried in a vacuum oven at 100 Torr (13 kPa) and 50° C. for 48hr. This gives 854 g (83% yield) of a white powder. The final product ispure (by ¹⁹F and ¹H NMR) since the undesired hydration product (Equation(2)) remains in the water during filtration. The aqueous layer isfreeze-dried to afford 325 g of material.

Analysis: calculated for C₃HF₆SO₄K: C, 12.6: H, 0.4: N, 0.0; Found: C,12.3: H, 0.7: N, 0.0.

This example shows that the desired adduct precipitates in good yield athigh purity. It can be used without further purification. Little of theadduct remains in the liquid layer (<17%).

Example 3 Synthesis of Potassium1,1,2-Trifluoro-2-(perfluoroethoxy)ethanesulfonate (TPES-K)

A 1-gallon reaction vessel made of Hastelloy C276 is charged with asolution of 88 g potassium sulfite hydrate (KHSO₃.H₂O, 95%, Aldrich,0.56 mol), 340 g potassium metabisulfite (K₂S₂O₅, 99%, Mallinckrodt,1.53 mol) and 2000 mL of deionized water. The vessel is cooled to 7° C.,evacuated to −7 psig (48 kPa), and purged with nitrogen. Theevacuate/purge cycle is repeated two more times. To the vessel is thenadded 600 g perfluoro(ethyl vinyl ether) (PEVE, 2.78 mol) and the vesselis heated to 125° C. at which time the inside pressure is 320 psig (2300kPa). The reaction temperature is maintained at 125° C. for 10 hr. Thepressure drops to 23 psig (260 kPa) at which point the vessel is ventedand cooled to 25° C. The crude reaction product is a white crystallineprecipitate with a colorless aqueous layer (pH=7) above it.

19F NMR of the white solid shows pure desired product. ¹⁹F NMR of theaqueous layer shows a small but detectable amount of the hydrationproduct shown in Equation (3).

The desired compound (C₂F₅O—CF₂H—CF₂—SO₃ ⁻K⁺) is less soluble in waterso it precipitates in pure form.

The product slurry is suction filtered through a fritted-glass funnel.The wet cake is dried in a vacuum oven (60° C., 100 Torr (13 kPa)) for48 hr. The product is obtained as off-white crystals (904 g, 97% yield).

¹⁹F NMR (D₂O) δ −86.5 (s, 3F); −89.2, −91.3 (subsplit ABq, ²J_(FF)=147Hz, 2F); −119.3, −121.2 (subsplit ABq, ²J_(FF)=258 Hz, 2F); −144.3 (dm,²J_(FH)=53 Hz, 1F).

¹H NMR (D₂O) δ 6.7 (dm, ²J_(FH)=53 Hz, 1H).

Melting point (DSC) 263° C.

Elemental Analysis calculated for C₄HO₄F₈SK: C, 14.3: H, 0.3; Found: C,14.1: H, 0.3.

TGA(air): 10% weight loss at 359° C. 50% weight loss at 367° C.

TGA(N₂): 10% weight loss at 362° C., 50% weight loss at 374° C.

NMR analysis of the liquid phase shows it to contain about 3% of theundesirable hydration product (Equation (3)).

Compared to the adduct of Example 2, the higher molecular weight adductof PEVE is less soluble and therefore precipitates in higher yield,obviating the need for further purification or further recovery ofwhatever small amount remains in the liquid phase.

Example 4 Synthesis of Adduct of Sodium Bisulfite and LithiumPerfluoro-3,6-dioxa-4-methyl-7-octenesulfonate

Example 4 shows the reaction of a functional vinyl ether. In this casethe product has a sulfonate group at both ends.

-   1. Synthesis of lithium salt of    perfluoro-3,6-dioxa-4-methyl-7-octenesulfonyl fluoride (PDMOF)

The reaction can be represented as:

To a 2-neck 50 mL flask is added 1.66 g (0.02 mol) lithium carbonate(Aldrich, >99%) and 10 mL dry methanol. The system is purged withnitrogen and cooled to 7° C. using an ice bath. PDMOF (10.0 g, 0.02 mol)is added dropwise via glass syringe over 20 minutes. No exotherm isobserved during this addition. The solution is allowed to warm to roomtemperature (20-25° C.) and stirred for 12 hr. Reaction is monitored by¹⁹F NMR and is complete when the signal for the fluorine bonded tosulfur (+43.4 ppm) is no longer observed.

The reaction solution is filtered through a 0.4 micron Teflon® PTFEsyringe filter to remove the lithium fluoride precipitate as well as anyremaining lithium carbonate. The methanol is removed in vacuo (60 mTorr(8 Pa), 25° C., 4 hr) to give 10 g of a waxy solid. The product stillcontains some methanol.

-   2. Reaction of Li-PMDOF with Sodium sulfite/bisulfite

The reaction can be represented as:

To a 100 mL flask is added 10 g of Li-PMDOF (0.02 mol), 2.3 sodiumbisulfite (0.02 mol), 0.6 g sodium sulfite (4.4 mmol), and 40 mLdeionized water. This mixture is stirred and heated to reflux for 2 hrusing an oil bath. An ¹⁹F NMR (D₂O) spectrum of the solution at thispoint shows complete conversion by the absence of any vinyl fluorinesignals. The aqueous solution (pH=7) is reduced in vacuo to give thecrude product as a white solid. The solid is dissolved in 50 mL ofspectrophotometric grade acetone (Aldrich) and stirred magnetically for12 hr. A small amount of insoluble material (˜2 g) is removed by suctionfiltration and the remaining acetone is removed in vacuo to give 12.0 g(0.22 mol) of white solid (97% yield).

Analysis. Calculated for C₇HO₈S₂F₁₃NaLi: C, 15.2: H, 0.2; N, 0.0; Found:C, 15.0: H, 1.2: N, 0.2.

Melting pt. (DSC) 135° C.

TGA (air): 10% weight loss at 360° C., 50% weight loss at 411° C.

TGA (nitrogen): 10% weight loss at 356° C., 50% weight loss at 394° C.

DSC is differential scanning calorimetry.

TGA is thermal gravimetric analysis.

Example 5 Synthesis ofTriphenylsulfonium-1,1,2-trifluoro-2-(perfluoroethoxy)ethanesulfonate(TPS-TPES)

TPS-TPES, potassium-1,1,2-trifluoro-2-(perfluoroethoxy)ethanesulfonate(29.4 g, 8.74×10⁻² mol), is dissolved in 600 mL of deionized water atroom temperature (RT) in a 1000 mL flask. In a separate 500 mL flask,30.0 g (8.74×10⁻² mol) of triphenylsulphonium bromide (TPS—Br, DayChem.Inc., Dayton, Ohio) is dissolved in 220 mL deionized water at 40° C.These two solutions are combined and stirred at RT for 3 hr, at whichpoint the product is observed as a light yellow oil on the bottom of theflask. The oil is removed and washed with 2×100 mL portions of deionizedwater. It is then dried in vacuo at 75 milliTorr (10 Pa) and 40° C. for1 hr, and then at 60 milliTorr (8 Pa) and 25° C. for 5 hr. The productis in the form of a light yellow oil (42.3 g, 86% crude yield). Theproduct crystallized as a white solid from this oil over the period ofseveral days (34.0 g, 69% yield).

¹⁹F NMR (d₆-DMSO) δ −87.4 (s, 3F); −89.5, −91.8 (subsplit ABq,J_(FF)=147 Hz, 2F); −122.4, −124.0 (subsplit ABq, J_(FF)=253 Hz, 2F);−143.9 (dm, J_(FH)=54 Hz, 1F). ¹H NMR (d6-DMSO) δ 6.5 (dt, J=54 Hz, J=7Hz, 1H); 7.8 (m, 15H).

Carbon Hydrogen (elemental) analysis; Found: C, 46.7: H, 2.7. meltingpoint (DSC)=74.9° C.

The results of the NMR and elemental analysis show the product to betriphenylsulfonium-1,1,2-trifluoro-2-(perfluoroethoxy)ethanesulfonate(TPS-TPES).

Example 6 Synthesis ofTriphenylsulfonium-1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate(TPS-TTES)

TPS-TTES, potassium-1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate,(25.0 g, 8.74×10⁻² mol) is dissolved in 200 mL of deionized water in a500 mL flask. In a separate 500 mL flask, 30.0 g (8.74×10⁻² mol) oftriphenylsulfonium bromide (TPS—Br, DayChem Inc.) is dissolved in 200 mLdeionized water. These solutions are heated to 40° C. with stirring for15 min to dissolve the solids. The two solutions are mixed while stillwarm, which resulted in an immediate milky white suspension as well as alight brown oil. This mixture is stirred for 16 hr at RT. The oil isseparated and the colorless aqueous (pH=4) layer is extracted withmethylene chloride (3×100 mL). The product oil is combined with themethylene chloride washes and this organic layer is further washed with50 mL of saturated sodium carbonate and then 50 mL of deionized water.This layer is dried over magnesium sulfate and reduced in vacuo toafford 43.7 g of a yellow oil (98% crude yield).

The desired product slowly crystallized from the oil to give a whitecrystalline solid.

¹⁹F NMR (CD₃CN, ref. CFCl₃) δ −58.8d, J_(FH)=4 Hz, 3F); −121.6 (m, 2F);−143.6 (dm, J_(FH)=54 Hz, 1F).

¹H NMR (CD3CN) δ 6.4 (dt, J_(HF)=7 Hz, J_(HF)=54 Hz, 1H); 7.8 (m, 15H).Carbon Hydrogen (elemental) Analysis: C, 49.0: H, 3.0. melting point(DSC) 63.7° C.

The results of the NMR and elemental analysis show the product to betriphenylsulfonium-1,1,2-trifluoro-2-(trifluoromethoxy)ethanesulfonate(TPS-TTES).

Example 7 Photoresist Prepared from a TPS-TPES Photoacid Generator (PAG)

A. Synthesis of TFE/NB—F—OH/PinAc/HAdA/MAdA Pentapolymer

A 4000 mL pressure vessel is charged with 695.4 g (2.398 mol) ofNB—F—OH, 25.1 g (0.146 mol) of PinAc, 77.4 g (0.282 mol) of HAdA, 10.7 g(0.049 mol) of MAdA, 60.4 g (0.840 mol) of THF and 381.6 g (2.578 mol)of Solkane® 365mfc. The vessel is closed and heated to 50° C. underagitation at 100 rpm. The vessel is then charged with TFE until thereactor pressure reached 180 psig (1.24 MPa), at which point about 86 g(0.860 mol) of TFE is expected to be in the solution at that pressureand temperature. The monomer composition at the beginning of the run,then, is targeted to be 23% TFE, 64% NB—F—OH, 4% PinAc, 8% HadA, and 1%MAdA (mol %) and the reactor contained 1336 g of solution, includingdissolved TFE. When the reaction temperature and pressure setpoints arereached, continuous flow of three solutions to the reactor is begun. Twoof these solutions contained the monomers and chain transfer agent (THF)and the third contained the initiator. The first monomer solutioncontained 711.9 g (2.455 mol) of NB—F—OH, 51.6 g (0.717 mol) of THF and125.4 g (0.847 mol) of Solkane® 365mfc. This solution is metered intothe reactor by means of an Isco series D high-pressure precision syringepump at a constant rate of 1.054 g/min for 720 min. The second monomersolution contained 122.8 g (0.714 mol) of PinAc, 378.1 g (1.380 mol) ofHAdA, 52.3 g (0.238 mol) of MAdA, 49.0 g (0.681 mol) of THF, 119.1 g(0.805 mol) of Solkane® 365mfc and 171.4 g (2.301 mol) of methyl acetateto aid in dissolution of the monomers. This solution is metered in asecond Isco series D high-pressure precision pump at a constant rate of1.088 g/min for 720 min. The initiator solution contained 89.2 g (0.224mol) of Perkadox® 16N, 369.7 g (2.498 mol) of Solkane® 365mfc and 518.9g (7.012 mol) of methyl acetate. The initiator solution is metered intothe reactor with an Isco series D high-pressure precision syringe pumpat 35.49 g/min for six min, followed by a rate of 1.42 g/min for 480min. TFE is supplied to the reactor over the course of 720 min bymaintaining the reactor pressure at 180 psig (1.34 MPa). The calculatedtotal amounts of ingredients added to the vessel after 720 min ofreaction is 275.7 g (2.757 mol) of TFE, 1287.9 g (4.441 mol) of NB—F—OH,132.3 g (0.769 mol) of PinAc, 407.5 g (1.487 mol) of HAdA, 56.4 g (0.256mol) of MAdA, 146.2 g (2.031 mol) of THF, 922.9 g (6.236 mol) ofSolkane® 365mfc, 602.3 g (8.139 mol) of methyl acetate and 81.6 g (0.205mol) of Perkadox® 16N. The reaction temperature is held at 50° C., thepressure is maintained with TFE feed at 180 psig (1.34 MPa), and theagitation rate is 100 rpm over the course of the 720 min of reaction.After 720 min, the TFE feed is stopped and the reactor is held underagitation for 4 hr at 50° C. The vessel is then cooled rapidly to roomtemperature and vented to 1 atmosphere. The vessel contents aretransferred to a container via blowcasing after adding an additional 400ml of THF to reduce viscosity and aid in rinsing of the vessel. A 1073.4g (890 ml) sample of the resultant polymer solution is metered into a22-L agitated flask containing 16020 ml of n-heptane (18/1 volume ratioto polymer solution). After mixing for 30 min, the slurry is dischargedacross an in-line cloth filter. The wet precipitate on the filterweighed 497.8 g. A sample of this precipitate (478.7 g.) is redissolvedwith 765.9 ml of Solkane® 365mfc and 480 ml of THF. The resultantsolution is precipitated a second time into a vessel containingn-heptane at a volume ratio of 18/1 with the polymer solution. Aftermixing for 30 min, the slurry is discharged again across another in-linecloth filter. The filtrate is dried under vacuum with a nitrogen bleedat 70° C. for 16 hr to obtain 347 g of very fine, white powder. Gelpermeation chromatography of the product indicated Mn=5130, Mw=9780 andMw/Mn=1.91. A combination of ¹³C and ¹⁹F NMR analyses of the productresulted in a calculated polymer composition of 15 mol % TFE, 39 mol %NB—F—OH, 10 mol % PinAc, 30 mol % HAdA and 6 mol % MAdA.

-   B. The following formulation is prepared and magnetically stirred    overnight:

Component Wt. (gm) TFE/NB-F-OH/PinAc/MAdA/HAdA Polymer 2.95(15/39/10/6/30) 2-Heptanone 20.63 Tetrabutylammonium lactate solutionprepared by 0.72 diluting a 1% (wt) solution of tetrabutylammoniumhydroxide solution in ethyl lactate (2.5 gm 40% (wt) aqueoustetrabutylammonium hydroxide + 97.5 gm ethyl lactate) with an equalweight of 2-heptanone 6.82 wt % solution of photoacid generator TPS-TPES0.88 from Example 3 dissolved in 2-heptanone that had been filteredthrough a 0.45 μm PTFE syringe filter.

The wafer is prepared by applying a hexamethyldisilazane (HMDS) primerlayer using a YES-3 vapor prime oven. A 100% HMDS adhesion promoter fromArch Chemical Co. is used. The oven is set to give a prime at 150° C.for 300 seconds.

The sample is spin coated using a Brewer Science Inc. Model-100CBcombination spin coater/hotplate on a 4″ (100 mm) diameter Type “P”,<100> orientation, silicon wafer. To prepare the coating, 2 ml of theabove solution, after filtering through a 0.45 μm PTFE syringe filter,is deposited and spun at 1500 rpm for 60 sec, and then baked at 150° C.for 60 sec.

248 nm imaging is accomplished by exposing the coated wafer to lightobtained by passing broadband UV light from an ORIEL Model-82421 SolarSimulator (1000 watt) through a 248 nm interference filter which passesabout 30% of the energy at 248 nm. Exposure time is 15 sec, providing anunattenuated dose of 3 mJ/cm2. By using a mask with 18 positions ofvarying neutral optical density, a wide variety of exposure doses aregenerated. After exposure, the exposed wafer is baked at 135° C. for 60sec.

The wafer is tray-developed for 60 sec in aqueous 2.38 wt %tetramethylammonium hydroxide (TMAH) solution (LDD-26W, Rohm & HaasElectronics, Marlborough, Mass.). This test generates a positive imagewith a clearing dose of 5.8 mJ/cm².

Example 8 Photoresist Prepared from a TPS-TTES Photoacid Generator (PAG)

A formulation is prepared as in Example 7, except that the photoacidgenerator used is that (TPS-TTES) prepared in Example 4. This testgenerates a positive image with a clearing dose of 4.9 mJ/cm².

1. A photoresist composition comprising a polymeric binder and acompound of the formula R—O—CXH—CX₂—SO₃M, wherein R is selected from thegroup consisting of alkyl groups, functionalized alkyl groups, andalkenyl groups; X is selected from the group consisting of hydrogen andfluorine with the proviso that at least one X is fluorine; and M isorganic onium.